Osteoarthritis (OA) is the most prevalent musculo-skeletal disease in the older adult population, characterized by chronic pain and life long disability. The current 'gold standard' for diagnosis of OA is radiology, but radiological changes occur relatively late in the disease after the bone tissue changes responsible for the pain and disability have already taken place. A diagnostic test that uses biomarkers of OA for early detection would be useful in early diagnosis and treatment, ameliorating symptoms and potentially lessening disability. The general goal of this project is to produce a microarray for detecting proteins in serum that are biomarkers of OA including cytokines and products of cartilage & bone catabolism In order to achieve sufficient sensitivity, this microarray will utilize a novel proprietary technology, rolling circle amplification, for signal amplification. The RCA-enabled microarray will offer the benefits of multiplexing (measuring approximately 100 analytes simultaneously), reduced sample volume (only 15 ul/assay), high-throughput, and exceptional sensitivity (ca. 10 pg/mI). Initial studies will be done with serum from patients with OA and appropriate controls using our current cytokine chip. We also will identify other reagents as potentially useful biomarkers for OA with the aim of designing an OA chip.